Cascade types and behavior in Spring Boot - Mini Project: Build & Apply

Cascade Types and Behavior in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage Authors and their Books. Each author can have multiple books. You want to understand how cascade types work so that when you save or delete an author, the related books are handled automatically.

🎯 Goal: Build two JPA entity classes Author and Book with a one-to-many relationship. Configure cascade types so that saving or deleting an author also saves or deletes their books.

📋 What You'll Learn

Create an Author entity with an id and name field

Create a Book entity with an id and title field

Set up a one-to-many relationship from Author to Book using @OneToMany

Add cascade type ALL to the relationship

Add orphanRemoval = true to remove books when they are no longer linked to an author

💡 Why This Matters

🌍 Real World

Managing related data entities like authors and books is common in library or publishing applications. Cascade types help keep data consistent automatically.

💼 Career

Understanding JPA cascade types is essential for backend developers working with Spring Boot and databases to manage entity relationships efficiently.

1

Create the Author entity

Create a Java class called Author annotated with @Entity. Add a private Long id field annotated with @Id and @GeneratedValue. Add a private String name field. Include public getters and setters for both fields.

Spring Boot

@Entity
public class Author {
    // Your code here
}

Need a hint?

Remember to import javax.persistence.Entity, Id, and GeneratedValue annotations.

2

Create the Book entity

Create a Java class called Book annotated with @Entity. Add a private Long id field annotated with @Id and @GeneratedValue. Add a private String title field. Include public getters and setters for both fields.

Spring Boot

@Entity
public class Book {
    // Your code here
}

Need a hint?

Make sure to add the same annotations as in Author for id and generate getters/setters.

3

Add one-to-many relationship with cascade

In the Author class, add a private List<Book> books field annotated with @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true). Initialize it as an empty ArrayList<>(). Add public getter and setter for books.

Spring Boot

@Entity
public class Author {
    @Id
    @GeneratedValue
    private Long id;
    private String name;

    // Your code here

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Need a hint?

Use java.util.List and java.util.ArrayList. Import javax.persistence.OneToMany and CascadeType.

4

Complete with bidirectional mapping (optional)

In the Book class, add a private Author author field annotated with @ManyToOne. Add public getter and setter for author. This completes the bidirectional relationship.

Spring Boot

@Entity
public class Book {
    @Id
    @GeneratedValue
    private Long id;
    private String title;

    // Add the author field with @ManyToOne annotation
    // Your code here
}

Need a hint?

Import javax.persistence.ManyToOne and add getter/setter for author.